1. Field of the Invention
The present invention relates to an apparatus and method for enlarging or reducing an image in an image processing system and, more particularly, to an apparatus and method for modifying an enlargement ratio or a reduction ratio of an image in real time by using a sampling technique.
2. Related Art
In image processing systems, such as a digital copier or a facsimile, it may be necessary to reduce or enlarge an image. In the facsimile, for example, if there is a difference in resolution between an input device (a scanner) and an output device (a printer), or if there is a difference in the size between an input sheet and an output sheet, the image is appropriately reduced. A first method for reducing the image proceeds as follows: a few reduction ratios are determined, a periodic pattern corresponding to each reduction ratio of a binary image is determined, and then a processed pixel and a discarded pixel are determined. In a second method, the position of the processed pixel from the binary image is calculated by using the reduction ratio, and then the discarded pixel and the processed pixel are determined.
The image reducing method using the binary image has a smaller quantity of processed data than that using an image prior to conversion to binary (that is, prior to conversion to an intermediate tone image) but distorts the image. The distortion of the image is due to the fact that a regular pattern generated by a binary conversion processing technique, such as dithering or error diffusion, is simply discarded when reducing the image. If 50% of the image is reduced in the horizontal and vertical directions by using an averaging technique, four adjacent pixels contained in at least two lines are needed to form one pixel of a reduced image. In other words, the formed pixel has an average value derived from the sum of the four pixels, and the reduced image is situated at a position corresponding to the four pixels. Therefore, it is difficult to process the image in real time.
The following U.S. patents are considered to be representative of the prior art relative to the invention disclosed herein: U.S. Pat. No. 5,646,741 to Horiuchi et al., entitled Image Processing Apparatus And Method Capable Of Smoothing Image Data In Accordance With An Image Enlargement/Reduction Ratio, U.S. Pat. No. 5,642,203 to Sawano et al., entitled Method Of Enlarging And Processing Image Data, U.S. Pat. No. 5,621,826 to Katayama et al., entitled Image Reduction Apparatus, U.S. Pat. No. 5,615,281 to Yamaguchi, entitled Method Of And Apparatus For Generating Reduced Image, U.S. Pat. No. 5,604,825 to Hirota et al., entitled Image Processing Apparatus Capable Of Varying Magnification Oc Images And Method Of Using Same, U.S. Pat. No. 5,566,005 to Yamada, entitled Image Reducing Apparatus Using Image division, Capable Of Adjusting Overlap In Recording, U.S. Pat. No. 5,555,557 to Mailloux, entitled Bit-Map Image Resolution Converter With Controlled Compensation For Write-White Xerographic Laser Printing, U.S. Pat. No. 5,553,201 to Muramatsu, entitled Digital Image Processing Device For Automatically Selecting One Of A Plurality Of Different Image Enlarging/Reducing Manners, U.S. Pat. No. 5,539,533 to Kato, entitled Facsimile Machine, U.S. Pat. No. 5,535,007 to Kim, entitled Method And Device For Adjusting Magnification Of Image, U.S. Pat. No. 5,511,137 to Okada, entitled Process And Apparatus For Image Magnification, U.S. Pat. No. 5,489,990 to Ishikawa, entitled Image Processing With Smooth Interpolation, U.S. Pat. No. 5,465,166 to Kamo, entitled Image Reading Device For Image Recording Equipment, U.S. Pat. No. 5,434,953 to Bloomberg, entitled Use Of Fast Textured Reduction For Discrimination Of document Image Components, U.S. Pat. No. 5,387,985 to Loce, et al., entitled Non-Integer Image Resolution Conversion Using Statistically Generated Look-Up Tables, U.S. Pat. No. 5,309,524 to Hirabayashi et al., entitled Image Reducing Apparatus, U.S. Pat. No. 5,309,253 to Ariga et al., entitled Image Enlargement/Reduction processor And Method, U.S. Pat. No. 5,280,365 to Nannichi et al., entitled Image Professor With Reduction Of Enlarged Image Data To Form Image Data Enlarged With A Desired Magnification, and U.S. Pat. No. 4,930,022 to Kubota, entitled Method And Device For Image Reduction In Image Processing.
Nevertheless, each of the above patents is burdened by one or more of the disadvantages discussed above, or by disadvantages which will be discussed in the succeeding paragraphs. Thus, there is a need in the prior art for provision of an apparatus and method for enlarging or reducing an image in an image processing system in accordance with the present invention.